The invention relates to a multispot grid-welding machine having an electrode-carrier beam which can be moved up and down in welding tempo and on which by means of guide rods a plurality of electrode units are moved, loaded by pressure-springs, in the direction towards the grid welding plane, and in which each electrode unit can be located in a retracted position of rest.
In multispot grid-welding machines of this type, known from AT-A- 325,393, the guide rods by means of which the electrode units are guided displaceably on the electrode-carrier beam are provided with stops, which cooperate with locking pins. If the electrode-carrier beam is lying in its lowest position, in which the electrode pressure-springs are compressed to their greatest amount, the guide rods of selected electrodes can be raised a little by the application of force by hand, by further compressing the electrode pressure-springs, and the associated locking pins can then be advanced under the stops on these guide rods until, upon subsequent raising of the electrode-carrier beam, relief of the pressure-springs in question is prevented. The selected electrodes then remain locked in a raised position of rest relative to the electrode-carrier beam, and upon lowering the electrode-carrier beam once more cannot come into contact with the work which is to be welded.
In this way it is possible to exclude selected electrodes from the welding process, for example, when grids must be produced with pitches of the longitudinal wires which amount to an integral multiple of the smallest pitch of the longitudinal wires, i.e., a basic spacing.
In the known machine the resetting of the electrodes, namely from the basic spacing to a multiple thereof by locking the electrodes not needed in the raised position during welding at the wider spacing, is possible only while the machine is at a standstill and only by hand, and the electrode-carrier beam must furthermore be lying in its lowest position. The resetting process is time-consuming, because the machine operator proceeding along the electrode-carrier beam, must in succession snap the locking pins into their active positions on all of the electrodes, which are to be excluded. Actuation of the locking pins is hardly possible if there is a grid in the machine, because the machine operator in this case cannot reach over to those locking pins which lie along the electrode-carrier beam at a greater distance than an arm's length from the edge of the grid. Finally, before locking an electrode, its guide rod must be raised a little against the whole considerable biasing force of the associated pressure-spring, in order to be able to bring the locking pin into its active position.
The invention has as its object the development of a multispot grid-welding machine in which the electrode units (which may be formed by single electrodes for single-spot welding, or by pairs of electrodes for double-spot welding, together with their associated electrode holders) may, even during operation of the machine, be brought selectively out of, or into a working position, in which they take part in the welding process, and into or out of, respectively, a position of rest, in which they do not participate in the welding process, without any additional stressing of the very powerful electrode pressure-springs being necessary.